I. Field of the Invention
The present invention relates to compositions which are useful as anti-oxidants, and in particular, for antioxidants used in lubricants.
II. Description of the Art
It is known from an article entitled The Condensation of 2-Hydroxyethylsulfides with Alcohols and Phenols by Richter et al, Journal of Polymer Science, Volume XLI, Pages 4076-4079, that a beta-dithiodialkanol when reacted in the presence of hydrochloric acid and an alcohol will give the corresponding ether as a reaction product. The technology in the Richter article is further reported in U.S. Pat. No. 2,582,605 issued Jan. 15, 1952.
It is suggested in German published patent application 1,520,040A that Guerbet alcohols may be condensed with thiodialkylols at a molar ratio of 1:0.5-0.9. U.S. Pat. No. 4,366,307 issued Dec. 28, 1982 to Singh et al describes non-crystallizing, water, solvent, fuel and temperature resistant liquid polythioethers having 2-4 terminating radicals and at least 8 repeating sulfur-containing units.
Reid, in U.S. Pat. No. 2,230,966, issued Feb. 4, 1941, describes compositions which are alkylthio diethylsulfides. Reid states these materials may be used in lubricants and particularly as transformer fluids.
Further information with regard to the polymerization of a beta-thiodialkanol is found in Thioglycol Polymers I Hydrochloric Acid-Catalyzed Auto Condensation of Thiodiglycol by Woodward, Journal of Polymer Science, Volume XLI, Pages 219-223 (1959). The hydroxyl groups in the beta position relative to the sulfur in an aliphatic chain are stated to be of unusual reactivity in the Woodward article. Further information on such beta-dialkanols is found in Thioglycol Polymers III Copolymerization of Thiodiglycol and Similar Thioglycols with Aliphatic Hydroxy Compounds by Andrews et al, Journal of Polymer Science, Volume XLI, Pages 231-239 (1959). The Andrews' reference describes copolymers obtained from dihydroxy compounds where one of the compounds is thiodiglycol.
U.S. Pat. No. 3,450,771 issued June 17, 1969 to Dombro describes organic sulfides that may be prepared by reacting a mercaptan, such as an n-octyl mercaptan, with an alcohol, such as methanol, in alkaline medium. Dombro further describes his process as being useful in removing mercaptans from petroleum products.
In an article Nucleophilic Substitution of Hydroxyl Groups in 2-Alkyl (Aryl)-Thioethanols, published by Fokin et al in the Bull. Acad. Sci. U.S.S.R. Div. Chem. Sci. 1982, Page 1667, there is described the homocondensation of 2-alkylthioethanols. It is also disclosed in the Fokin paper that the 2-alkylthioethanol may be reacted with an alcohol to give a product containing both sulfur and ether linkages. Aromatic sulfur-containing compounds containing beta-hydroxy groups and their reaction properties are also discussed in the Fokin article. The Fokin paper does not discuss any particular utility or special advantage for the compositions described therein.
Musser and Koch in U.S. Pat. No. 4,031,023 issued June 21, 1977 describe lubricating compositions which utilize hydroxy thioethers, methods of using these materials in lubricating compositions, and additive concentrates for forming such lubricant compositions. The compositions of Musser and Koch show terminal mercaptan and terminal hydroxy groups thereon.
It has been determined in accordance with the present invention that various products may be prepared from thiodialkanols which are reacted with a mercaptan. It is further described herein that beta-thiodialkanols may be polymerized, and the terminal hydroxyl groups on the polymerized thiodialkanol capped with the mercaptan as is later described.
The compositions of the present invention are particularly effective as anti-oxidants in lubricant compositions, and are capable of functioning in specialized uses as a lubricant per se with exceptional anti-oxidant properties.
Throughout the specification and claims, percentages and ratios are by weight, temperatures are in degrees Celsius, and pressures are expressed in KPa gauge unless otherwise indicated.